AQUATIC AND SHORE HABITAT OF MILLE LACS LAKE, MINNESOTA 2009 to 2019 Report by: Stephanie Simon1, Donna Perleberg2, and Paul Radomski3 Minnesota Department of Natural Resources Ecological and Water Resources (EWR) Division Lake Ecology Unit 1601 Minnesota Drive, Brainerd, MN 56401 COPYRIGHT Minnesota Department of Natural Resources 2020 Aquatic and Shore Habitat of Mille Lacs Lake, Minnesota 2009-2019 SURVEYORS: 2009: Donna Perleberg, Stephanie Simon, Kevin Mortensen5, Adam Rollins6 2010: Donna Perleberg, Stephanie Simon, Zack VanDyne7, Nick Whichello8 2014: Stephanie Simon, Josh Knopik4, Donna Perleberg, Colby Seaberg9, Kassandra Franke8 2017: Stephanie Simon, Josh Knopik, Courtney Sullivan8, Angela Les5 2019: Stephanie Simon, Josh Knopik, Paul Radomski, Timothy Paquin8, Tre Winchester10 1Aquatic Biologist, MNDNR EWR, Lake Ecology Unit, Bemidji, MN Phone: 218-308-2465 email: [email protected] 2Aquatic Plant Ecologist, MNDNR EWR, Lake Ecology Unit, Brainerd, MN Phone: 218-203-4363 email: [email protected] 3Research Scientist, MNDNR EWR, Lake Ecology Unit, Brainerd, MN Phone: 218-203-4361 email: [email protected] 4Aquatic Ecologist, MNDNR EWR, Lake Ecology Unit, Brainerd, MN 5Aquatic Plant Survey Intern (University of Minnesota, St. Paul, MN) 6Aquatic Plant Survey Intern (Central Lakes College, Brainerd, MN) 7Aquatic Plant Survey Intern (St. Cloud State University, St. Cloud, MN) 8Aquatic Plant Survey Intern (Bemidji State University, Bemidji, MN) 9Aquatic Plant Survey Intern (Michigan Technical University, Houghton, MI) 10Aquatic Plant Survey Intern (Green River College, Auburn, WA) Acknowledgements: We thank the following reviewers for their careful reading and insightful comments that helped improve this report: Eric Jensen, Gary Montz, and Steve Kloiber. We would also like to thank the numerous surveyors who assisted on this project including Adam Pangrac and Jennifer Hardy (MNDNR Watercraft Inspection Interns) for their field survey assistance in 2009. We remember Dr. David Wright and are grateful that he encouraged us to pursue this project, asked challenging questions and was always interested to learn about our findings. Copyright MNDNR 2020 Page 2 of 103 Aquatic and Shore Habitat of Mille Lacs Lake, Minnesota 2009-2019 TABLE OF CONTENTS TABLE OF CONTENTS .............................................................................................................................................. 3 EXECUTIVE SUMMARY ........................................................................................................................................... 5 CHAPTER 1. OVERVIEW AND LAKE DESCRIPTION OF MILLE LACS LAKE .................................................................. 8 INTRODUCTION .............................................................................................................................................................. 8 OVERVIEW OF REPORT .................................................................................................................................................... 8 LAKE DESCRIPTION ......................................................................................................................................................... 8 Lake physical characteristics ................................................................................................................................. 9 Environmental factors influencing plant growth in Mille Lacs .............................................................................. 9 Non-native aquatic animal species ..................................................................................................................... 10 AQUATIC VEGETATION OF MILLE LACS ............................................................................................................................. 11 Historical plant data ........................................................................................................................................... 11 Non-native aquatic plants ................................................................................................................................... 11 Rare plants .......................................................................................................................................................... 12 TABLE 1.1. INDEX OF SURVEY METHODS USED IN EACH AREA OF MILLE LACS ............................................................................ 14 TABLE 1.2. AQUATIC PLANTS OBSERVED IN MILLE LACS LAKE FROM 1918 TO 2019 .................................................................. 15 CHAPTER 2. LAKE SHORE HABITAT (SCORE THE SHORE) ...................................................................................... 25 INTRODUCTION ............................................................................................................................................................ 25 METHODS ................................................................................................................................................................... 26 Land Use .............................................................................................................................................................. 26 Habitat Features ................................................................................................................................................. 26 RESULTS ..................................................................................................................................................................... 27 Land Use .............................................................................................................................................................. 27 Habitat Scores ..................................................................................................................................................... 30 Comparison of Mille Lacs Shore Habitat with other Minnesota lakes ................................................................ 32 DISCUSSION ................................................................................................................................................................ 33 CHAPTER 3. EMERGENT AND FLOATING-LEAF PLANT STANDS ............................................................................. 36 INTRODUCTION ............................................................................................................................................................ 36 METHODS ................................................................................................................................................................... 36 RESULTS ..................................................................................................................................................................... 37 DISCUSSION ................................................................................................................................................................ 38 TABLE 3.1. EMERGENT AND FLOATING-LEAF PLANT STAND ACRES .......................................................................................... 39 TABLE 3.2. EMERGENT AND FLOATING-LEAF PLANTS OBSERVED IN EACH BAY ............................................................................ 39 CHAPTER 4. SUBMERGED PLANT COMMUNITIES (POINT-INTERCEPT SURVEYS) .................................................. 44 INTRODUCTION ............................................................................................................................................................ 44 METHODS ................................................................................................................................................................... 44 Macroplot Selection ............................................................................................................................................ 44 ESTABLISHMENT OF BASELINE (2009) SAMPLE SITES FOR POINT INTERCEPT SURVEYS ................................................................ 45 Sampling site density .......................................................................................................................................... 45 Water depths sampled ........................................................................................................................................ 45 Copyright MNDNR 2020 Page 3 of 103 Aquatic and Shore Habitat of Mille Lacs Lake, Minnesota 2009-2019 DATA ANALYSIS ........................................................................................................................................................... 46 RESULTS – 2009 BASELINE DATA ..................................................................................................................................... 48 nearshore shallow substrates ............................................................................................................................. 48 PLANT COMMUNITIES ................................................................................................................................................... 49 ZEBRA MUSSELS ........................................................................................................................................................... 62 DISCUSSION ........................................................................................................................................................